In order to manufacture a desired semiconductor device, various vacuum processes including a CVD film-forming process and/or a plasma etching process are carried out to a substrate to be processed, for example a semiconductor wafer. In such a process, the semiconductor wafer has to be heated to a predetermined temperature. Thus, a heater is used to heat a substrate-supporting member.
As such a heater, a stainless-steel heater or the like is used conventionally. However, recently, a ceramic heater has been spread because it has high corrosion resistance against a halogen gas used in the process and high thermal efficiency. The ceramic heater has a base body serving as a stage for placing a substrate to be processed thereon and a heat-generating body buried in the base body. The base body may be made of a dense sintered ceramic such as AIN. The heat-generating body may be made of high-melting-point metal.
A substrate-processing apparatus including the ceramic heater as a substrate-placing stage is disclosed in JP Laid-Open Publication No. 2001-160479 (Patent Document 1). In the substrate-processing apparatus disclosed in the Patent Document 1, a ceramic heater serving as a substrate-placing stage is supported by a supporting body that stands up at a base of a processing container. In the supporting body, a feeder line for feeding electric power to the heat-generating body of the ceramic heater is provided. The feeder line is connected to feed terminals for the heat-generating body, which are arranged on a lower surface of the ceramic heater. Thus, the heat-generating heater is fed the electric power from the outside electric power supply source through the feeder line and the feed terminals.
As the feeder line, a rod-like feeder line, i.e., a feed rod is used. In general, the feed rod is made of a nickel alloy or the like, and has high heat resistance. The feed rod and the feed terminals are connected by a mesh wire. At a lower-end portion of the supporting body, the feed rod is fixed to connection terminals for being connected to the power supply source, for example by means of screws.
Herein, recently, the size of the semiconductor wafer has been shifted from 200 mm to 300 mm, and thereby the size of the substrate-processing apparatus has been also increased. If the size of the substrate-processing apparatus is large, it is impossible to ignore thermal expansion of the feed rod when the semiconductor wafer is heated by the ceramic heater. That is, breaking or the like at a feed member such as a feed wire may be caused by repetition of heating.